信號發(fā)生器的基本知識概述

1、Source Basics Copyright 2000AgendalTypes of sourceslCWlSweptlSignal GeneratorlBlock DiagramslApplicationslSpecificationsSource Basics Copyright 2000Sources Generate Sine WavesVoltageTimeVoltageFrequencyThis is the ideal output: most specs deal with deviations from the ideal and adding modulation to

2、a sine waveRFMicrowaveMillimeter20-50 GHz300 GHz3-6 GHzSpectrum AnalyzerOscilloscopeSource Basics Copyright 2000Types of SourceslCWgenerates a single frequency, fixed sine wavelSweptsweeps over a range of frequenciesmay be phase continuouslSignal Generatoradds modulationproduces “real world” signalS

3、ource Basics Copyright 2000AgendalTypes of sourceslCWlSweptlSignal GeneratorlBlock DiagramslApplicationslSpecificationsSource Basics Copyright 2000CW Source Specifications.FrequencyVoltageFrequencyUncertaintylRange: Range of frequencies covered by the sourcelResolution: Smallest frequency increment.

4、lAccuracy: How accurately can the source frequency be set.EXAMPLEAccuracy = =CW frequency = 1 GHz=aging rate = 0.152 ppm/year=time since last calibrated = 1 year +_fCWtagingcalt*fCWtagingcaltAccuracy = 152 Hz+_Source Basics Copyright 2000CW Source Specifications.AmplitudeDUTSource protected from acc

5、idental transmission from DUTVoltageFrequencyHow accurate is this number?What is P out?What is P out?maxminlRange (-136dBm to +13dBm)lAccuracy (+/- 0.5dB)lResolution (0.02dB)lSwitching Speed (25ms)lReverse Power ProtectionSource Basics Copyright 2000lPhase NoiselResidual FMlSpuriousCW Source Specifi

6、cations.Spectral Puritynon-harmonic spur65dBcharmonic spur30dBcCW outputResidual FM is the integrated phase noise over 300 Hz - 3 kHz BWphase noise 0.5 f0 f0 2f0sub-harmonicsSource Basics Copyright 2000CW Source Specifications. Spectral Purity: Phase NoiseCW outputfrequencyPower Spectral Densitymeas

7、ured as dBc/HzCh1 PM PSD1k10k100kTRACE A:A Marker 10 000 Hz75 dBc/Hz-125 dBc/HzLogMag 5 dBc/div-105 dBc/HzSource Basics Copyright 2000RF CW Block DiagramReferenceOscillatorfVCOPhaseDetectorFrac-Ndivideby XALC ModulatorALCDriverALC DetectorOutputAttenuatorALC = automatic level controlReference Sectio

8、nSynthesizer SectionOutput SectionSource Basics Copyright 2000RF CW Block DiagramReference SectionfPhaseDetectorOptional External Reference InputReference Oscillator (TCXO or OCXO) TCXOOCXOAging Rate+/- 2ppm/year+/- 0.1 ppm /yearTemp.+/- 1ppm+/- 0.01 ppmLine Voltage+/- 0.5ppm+/- 0.001 ppmto synthesi

9、zer sectiondivideby XSource Basics Copyright 2000RF CW Block DiagramSynthesizer SectionfVCOPhaseDetectorFrac-Nfrom reference sectionto output sectionX 2multiplierFront panelcontrol5MHz465.5 MHzN = 93.1931 MHz5MHduces accurate, clean signalsSource Basics Copyright 2000RF CW Block DiagramSynthesi

10、zer Sectionreferenceoscillatorphase noise of sourceVCO noisephase detector noisebroadband noise floor20logNphase-locked-loop (PLL) bandwidth selected for optimum noise performancePLL / Fractional - N.suppresses phase noisefrequencynoiseSource Basics Copyright 2000RF CW Block DiagramOutput SectionALC

11、 = automatic level controlALC ModulatorALCDriverALC DetectorOutputAttenuatorfrom synthesizer sectionsource outputlALCmaintains output power by adding/subtracting power as neededlOutput Attenuatormechanical or electronicprovides attentuation to achieve wide output range (e.g. -136dBm to +13dBm)Source

12、 Basics Copyright 2000mWave CW Block DiagramALC DetectorALC ModulatorALCDriverOutputAttenuatorSamplerReference SectionSynthesizer SectionOutput SectionRef OscfVCOPhaseDetFracNby XfVCOPhaseDetectorFrac-NfPhaseDetectorTuningCoilsYIGOscillatorSource Basics Copyright 2000Applications & Critical Spec

13、ificationslLocal Oscillatorphase noisefrequency accuracylAmplifier DistortionspuriousTOI (for system)lReceiver TestingSpurious spurious level accuracySource Basics Copyright 2000Applications & Critical SpecificationsAs a Local OscillatorIF signaltransmitter outputpoor phase noise spreads energy

14、into adjacent channelspoor frequency accuracy will cause transmitter to be at the wrong frequencyDUTSource Basics Copyright 2000Applications & Critical SpecificationsAmplifier Testingf2f1fU = 2f2 - f1fL = 2f1 - f2spurious signals from source can corrupt measurementfrequencyamplitudetest system t

15、hird order products will also fall hereoutput RFisolatorf1f2DUTIntermodulation DistortionSource Basics Copyright 2000Applications & Critical SpecificationsReceiver TestingIF Rejection CurveFrequencyLevel (dBm)spur from source and/or high levels of phase noise can cause a good receiver to failsou

16、rce outputIF signalin-channel signal(modulated signal)out-of-channel signal(CW or modulated signal)DUTReceiver SelectivitySource Basics Copyright 2000Agilent Families of CW GeneratorsRFMicrowaveAgilent 8664/65 familyl 100 MHz - 6 GHzl Low out channel noisel AM/FM/Pulse.Agilent 8662/63 familyl 100 KH

17、z - 2.5 GHzl Low in channel noisel AM/FM/Phase/PulseAgilent 83711/12B familyl 10 MHz - 20 GHzl CW onlySource Basics Copyright 2000AgendalTypes of sourceslCWlSweptlSignal GeneratorlBlock DiagramslApplicationslSpecificationsSource Basics Copyright 2000Sweeper Specifications.Frequencylramp sweepaccurac

18、ysweep timeresolutionlstep sweepaccuracynumber of pointsswitching timetimefrequencyf2t2t1f1t4t3t1t2f4f3f1f2frequencySource Basics Copyright 2000Sweeper Specifications.AmplitudeFrequency SweeplLevel AccuracylFlatnesslSource Match (SWR)Power SweeplPower Sweep RangelPower Slope RangelSource Match (SWR)

19、flatness speclevel accuracy specf1f2frequencypowerpowerP2P1power sweep ranget1t2Source Basics Copyright 2000Applications & Critical SpecificationslFrequency ResponseFrequency AccuracyOutput Power (Level) AccuracyFlatnessSpeedresidual FMlAmplifier CompressionPower RangeSource Basics Copyright 200

20、0Applications & Critical SpecificationsFrequency Response TestingLOSweeper InputlFrequency AccuracylOutput Power (Level) AccuracylFlatnesslSpeedlresidual FMSource Basics Copyright 2000Applications & Critical SpecificationsFrequency Response TestingCenter 2 450.212 MHz Span 1 099.577 MHz11356

21、 BW: 429.600 MHz CF: 2405.782 MHz Q: 5.60Loss: -0.84 dB1:TransmissionLog Mag 5.0 dB/Ref -15.00 dB -35 -30 -25 -20 -10 -5 0 5AbsdB Ch1Who Cares About Accuracy?Source Basics Copyright 2000Applications & Critical SpecificationsAmplifier CompressionPower InPower Out1 dB compressionpointThe 1 dB comp

22、ression point is a common amplifier specification used to identify the linear operating range of an amplifier. Power sweep is available on some Agilent sources.lPower RangeSource Basics Copyright 2000Synthesized Sweep Generators6Agilent 83750 Series Step/Analog sweepAM/FM/Phase modulation 10MHz to 2

23、0GHzup to 110GHz with 83550 series modules and amplifier 6Agilent 8360L Series Step/Analog sweep8510/8757 Compatibility 10MHz to 50GHzup to 110GHz with 83550 series modulesSource Basics Copyright 2000AgendalTypes of sourceslCWlSweptlSignal GeneratorlBlock DiagramslApplicationslSpecificationsSource B

24、asics Copyright 2000Signal GeneratorslCalibrated modulationAnalog (AM, FM, PM, Pulse)Digital (I-Q)Format Specific(TDMA,CDMA, etc.)Source Basics Copyright 2000Modulation.Where the information residesAM, PulseFMPMqV= A(t) sin (t)pV= A(t) sin2 f(t) + (t)fSource Basics Copyright 2000Modulation: AnalogAm

25、plitude ModulationImportant Signal Generator Specs for Amplitude ModulationVoltageTimeCarrierModulationlModulation frequencylLinear AMlLog AMlDepth of modulation (Mod Index)Source Basics Copyright 2000Modulation: AnalogFrequency ModulationVoltageTimeImportant Signal Generator Specs for Frequency Mod

26、ulationV= A sin2 f t + m(t)pcbF /Fdevmodb = DlFrequency DeviationlModulation FrequencyldcFMlAccuracylResolutionSource Basics Copyright 2000Modulation: AnalogPhase Modulationb = Df peakV= A sin2 p f t + m(t)Important Signal Generator Specs for Phase ModulationlPhase deviationlRateslAccuracylResolutio

27、nVoltageTimecbSource Basics Copyright 2000Modulation: AnalogPulse ModulationTimePulseOn/Off ratioRisetimeRate=1/TTWidthPowert1/t1/TPowerImportant Signal Generator Specs for Pulse ModulationlPulse widthlPulse periodlOn/Off ratiolRise timeSource Basics Copyright 2000Digital Modulation.signal character

28、istics to modifyAmplitudeFrequency PhaseBoth Amplitudeand PhaseSource Basics Copyright 2000Digital ModulationPolar Display: Magnitude & Phase Represented TogetherlMagnitude is an absolute valuelPhase is relative to a reference signalPhaseMag0 degSource Basics Copyright 2000Digital ModulationSign

29、al Changes or ModificationsPhaseMag0 degMagnitude ChangePhase0 degPhase ChangeFrequency ChangeBoth Change0 deg0 degSource Basics Copyright 2000Digital Modulation.Binary Phase Shift Keying (BPSK)fV= A sin2 ft + (t) (t) =f1f2pfSource Basics Copyright 2000Digital ModulationBPSK IQ DiagramIQ01One Bit Pe

30、r SymbolSymbol Rate = Bit RateSource Basics Copyright 2000Digital Modulation.Quadrature Phase Shift Keying (QPSK)V= A sin2 ft + (t)f (t) =f1 = 3 /4pf2 = /4pf3 = - /4pf4 = - 3 /4ppfSource Basics Copyright 2000Digital ModulationQPSK IQ DiagramIQ00011011Source Basics Copyright 2000Digital Modulationp/4

31、 DQPSK IQ DiagramIQSource Basics Copyright 2000Digital ModulationModulation AccuracyIQMagnitude Error (IQ error mag)Error VectorIdeal (Reference) SignalPhase Error (IQ error phase)TestSignalf fSource Basics Copyright 2000Digital Signal Generator Block DiagramIQ Modulatormodulation qualityBaseband Ge

32、neratormodulation qualityadjacent channel performancesupported modulation formatsreference section (supplies timing)to output sectionSource Basics Copyright 2000Digital ModulationPSK Implementation: IQ Methodp p/2CarrierlGood Interface with Digital Signals and CircuitslCan be Implemented with Simple

33、 CircuitslCan be Modified for Bandwidth EfficiencyI:Q:Source Basics Copyright 2000Digital Signal Generator Block DiagramIQ Modulatorp p/2DACDACExt IExt Qfrom synthesizer sectionto output sectionQ from Baseband GeneratorI from Baseband GeneratorSource Basics Copyright 2000Digital Signal Generator Blo

34、ck DiagramBaseband GeneratorDACDACPattern RAMConstellation Map and Baseband FiltersTimingDataData ClockSymbol ClockFrom CPUIQAnalog Reconstruction FiltersSource Basics Copyright 2000Digital Signal GeneratorFormat Specific Digital SignalsNADC (TDMA IS-54) ParameterSpecificationAccess MethodTDMA/FDDMo

35、dulationp/4 DQPSKChannel Bandwidth30 kHzReverse Channel Frequency Band824 - 849 MHzForward Channel Frequency Band869 - 894 MHzFiltering0.35 RRCSource Basics Copyright 2000Digital Signal GeneratorAccess and Framingone frame = 1944 bits (972 symbols) = 40ms; 25frames/sec slot 1 slot 2 slot 3 slot 4 sl

36、ot 5 slot 6324 bit (162 symbols) = 6.667ms G R Data Sync Data SACCH CDVCC Data 6 6 16 28 122 12 12 122Mobile to Base StationSource Basics Copyright 2000Applications and Critical SpecificationsAnalog and DigitallReceiver Sensitivityfrequency accuracylevel accuracyerror vector magnitudelReceiver Selec

37、tivityphase noisespuriousspectral accuracylSpectral RegrowthACP performanceSource Basics Copyright 2000Applications and Critical SpecificationsReceiver Sensitivity Want to measuresensitivity in a channelMeasurement impaired by frequency inaccuracyfrequency inaccuracyamplitude inaccuracyinput for sig

38、nal generatorDUTlFrequency AccuracySource Basics Copyright 2000Applications and Critical SpecificationsReceiver Sensitivity Customer is testing a -110 dB sensitivity pager:Power Out -110 dB specificationCase 1: Source has +/-5 dB ofoutput power accuracy at-100 to -120 dBm output power.Set source to -115 dBmActual output power= -114 dBmXXX XXOCase 2: Source has +/-1 dB ofoutput power accuracy at-100 to -120 dBm output power.Power Out -110 dB specificationSet source to -111 dBmActual output power= -112 dBmXXO OOOX= Failed unitO=Passe